Use of 1,1&#39;-bis-(1-glycidoxylalkyl) ferrocenes in rocket propellants

ABSTRACT

1,1&#39;&#39;-Bis(1,glycidoxyalkyl)ferrocenes are new compounds prepared by (a) reacting an acyl halide with ferrocene to form a 1,1&#39;&#39;bis(acyl)ferrocene, (b) reducing the 1,1&#39;&#39;-bis(acyl)ferrocene to a 1,1&#39;&#39;-bis(1-hydroxyalkyl)ferrocene with a reducing agent, (c) reacting the 1,1&#39;&#39;-bis(1-hydroxyalkyl)ferrocene with an alkali metal alkyl to form the alkali metal salt, and (d) reacting the alkali metal salt with an epihalohydrin to form the final product. The 1,1&#39;&#39;-bis(1-glycidoxyalkyl)ferrocenes are useful as curing agents for solid rocket propellant binders, as plasticizers for solid rocket propellants, and as burn rate catalysts.

United States Patent 1191 Corley et a1.

[ USE OF 1,1'-BlS-(l-GLYCIDOXYLALKYL) FERROCENES IN ROCKET PROPELLANTS [75] Inventors: Robert C. Corley, Lancaster, Calif.;

Fred M. Dewey, Denver, C010.

[73] Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, DC.

22 Filed: Apr. 7, 1970 211 Appl. No: 31,041

[52] U.S. Cl 149/5, 149/7, 149/19.2, 149/44, 260/348 R, 260/439 CY [51] Int. Cl C06b 19/02 [58] Field of Search 260/348 R; 149/5, 7, 19, 149/l9.2

[56] References Cited UNITED STATES PATENTS 3,437,634 4/1969 Neuse 260/47 3,598,850 8/1971 Dewey 260/439 OTHER PUBLICATIONS Adams et 211., Organic Reactions, Vol. 17, John Wiley 1451 Apr. 1, 1975 & Sons, Inc., New York, 1969, pp. 1 to 5, OD 251 07.

Primary ExaminerLeland A. Sebastian Attorney, Agent, or Firm-Harry A. Herbert, Jr.; Cedric H. Kuhn [57] ABSTRACT 1,1'-Bis(1,glycidoxyalkyl)ferrocenes are new compounds prepared by (a) reacting an acyl halide with ferrocene to form a 1,1 '-bis(acyl)ferrocene, (b) reducing the 1,1'-bis(acy1)ferrocene to a 1,1'-bis(1- hydroxya1ky1)ferrocene with a reducing agent, (c) reacting the l,1-bis(1-hydroxyalkyl)ferrocene with an alkali metal alkyl to form the alkali metal salt, and (d) reacting the alkali metal salt with an epihalohydrin to form the final product. The 1,1 -bis( l-glycidoxyalkyl)- ferrocenes are useful as curing agents for solid rocket propellant binders, as plasticizers for solid rocket propellants, and as burn rate catalysts.

4 Claims, N0 Drawings USE OF 1,1 -BIS-(1-GLYCIDOXYLALKYL) FERROCENES IN ROCKET PROPELLANTS I RIGHTS OF THE GOVERNMENT The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to new ferrocene compounds and to a method for their preparation. In one aspect it relates to solid rocket propellants containing the ferrocene compounds.

2. Description of the Prior Art Ferrocene derivatives have been suggested for use as combustion catalysts for rocket propellants. However, the use of such compounds has not been satisfactory because, in general, the prior art ferrocene derivatives have been low molecular weight, highly volatile compounds. And when they have been incorporated into rocket propellants, they have exhibited a strong tendency to migrate away from the propellant grain into other parts of the rocket engine during storage. Thus, the search has gone on for new ferrocene derivatives which retain desirable properties, e.g., the ability to catalyze combustion, and which may be utilized in solid rocket propellants without exhibiting a tendency to migrate.

"-H II o H Fe SUMMARY OF THE INVENTION A class of ferrocene derivatives which may be utilized in solid rocket propellants without migration has now been discovered. The ferrocene derivatives of this invention have two epoxy groups per molecule which provide reactive sites which enable them to be chemically tied to solid propellant grains in several ways and thus prevent migration while a propellant containing them is in storage. The general formula of the compounds is:

wherein R is selected from the group consisting of hydrogen and alkyl. The alkyl group generally contains from 1 to 8 carbon atoms, preferably from 1 to 2 carbon atoms. They are prepared from ferrocene utilizing the following reactions wherein R is the same as above:

acyl halide LtalLSL R E; u v O alkali metal alkyl epihalohydr'in M in the above formulas is a symbol designating an alkali metal ion such as Li*, Na, or K. Methods of chemically tieing the compounds to solid propellant grains include (a) utilizing them as curing agents for hydroxy or carboxy terminated propellant binders, (b) precipitating them as homopolymer coats on oxidizer crystals prior to the incorporation of the crystals into solid propellant grains, and (c) introducing them as liquid plasticizers during the propellant mix cycle wherein they homopolymerize into high molecular weight, nonmigrating compounds.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preparation of the ferrocene derivatives of this invention may be conveniently described by selecting a specific compound and describing its preparation. The preparation of l, 1 '-bis( l-glycidoxyethyl)ferrocene is described in EXAMPLES I-IV below. It will be obvious to those skilled in the art that other similar derivatives may be prepared by substituting other acyl halides for the acetyl halide of EXAMPLE I.

EXAMPLE I STEP 1 1,1'-Bis(acetyl)ferrocene is prepared by reacting acetyl chloride with ferrocene in the presence of aluminum chloride. A ratio of 1 equivalent of ferrocene to 3 equivalents of acetyl chloride and 3 equivalents of the aluminum chloride catalyst are mixed in dry methylene chloride under a nitrogen atmosphere. The mixture is refluxed for about 18 to 24 hours and then hydrolyzed with de-oxygenated water and extracted with chloroform. Needles of 1,1-bis(acetyl)ferrocene form in and separate from the chloroform. When the needles are filtered out of the chloroform, washed with dilute sodium carbonate, and dried over anhydrous sodium sulfate, a yield of about 70% of theoretical of l,l'-bis- (acetyl)ferrocene is obtained.

EXAMPLE II STEP 2 1,1 '-Bis( l-hydroxyethyl)ferrocene is prepared by mixing 1,1 -bis(acetyl)ferrocene 15.0 g, 0.0555 mole) and lithium aluminum hydride (1.5 g) in 120 ml of dry tetrahydrofuran. The mixture is stirred and refluxed for about 1 to 2 hours. After refluxing, ethyl acetate is added to destroy any excess lithium aluminum hydride. Then a mixture of 3.5 ml water, 25 ml ethanol, and 50 ml ether is cautiously added to the mixture and the mixture is filtered. The filtrate is then subjected to reduced pressure to remove solvents. After removal of the solvents, 1,1'-bis(l-hydroxyethyl)ferrocene which remains as an oil is taken up in hot hexane. Cooling of the hexane solution in a dry ice bath yields about 70% of theoretical of 1,1 '-bis( l-hydroxyethyl)ferrocene needles which are separated from the hexane by filtration.

EXAMPLE III STEP 3 To prepare the lithium salt of l,l-bis(l-hydroxyethyl)ferrocene, the alcohol (0.5 g, 1.8 m moles) is dissolved in 20 ml of tetrahydrofuran and treated with 7.8 m moles of n-butyllithium (22.7 weight percent in hexane). The lithium salt of 1,1 -bis( l-hydroxyethyl)ferrocene which forms is left in the reaction mixture for use in the final step of the process.

EXAMPLE IV STEP 4 The final step in the preparation of l,1'-bis(lglycidoxyethyl)ferrocene is the addition of epibromohydrin (3.2 g, 20 m moles) to the reaction mixture of EXAMPLE Ill. The epibromohydrin is added dropwise and followed by the addition of ml of dimethylsulfoxide. The mixture is then refluxed for from 5 4 to 5 hours, poured onto ice, and extracted with ether.

A solution of the product in ether forms a layer separate from the rest of the mixture and is separated therefrom. The ethereal solution is washed first with water and then with a saturated sodium chloride solution and then dried over magnesium sulfate. The ether is then evaporated under reduced pressure. Column chromatography on alumina (hexane) gives an orange oil (0.4 g, 57 percent of theoretical): nmr(CDCl 4.38 (quartet, J= 6.5, 2H, C li(CH )--O), 4.14 (8H, ring protons), 3.54 (multiplet, 4l-l, OCl-I 3.10 (multiplet, 2H, epoxy CH), 2.67 (multiplet, 4H, epoxy CH and 1.53 ppm (doublet of doublets, J= 6.5 and 2, 6H, CH Analysis: Calculated for C l-I FeO C, 62.19; H, 6.79. Found: C, 61.82; H, 6.82.

The above EXAMPLES describe the preparation of 1,1 '-bis( 1-glycidoxyethyl)ferrocene, a compound wherein the R of the general formula is a methyl group. Other derivations wherein R is H, C I'I C l-l C I-I C ll C H, C l-l and C 11 may be prepared by substituting respectively O O O 0 U U U c ir j e-x,

and

wherein X is a halide such as C1 or Br for the acetyl chloride of EXAMPLE 1. Any desirable isomer of the alkyl group may be used. Other Lewis acids may be used as catalysts in lieu of the aluminum chloride of EXAMPLE 1. Other reducing agents such as sodium borohydride may be used in lieu of the lithium aluminum hydride of EXAMPLE I]. Other alkali metal alkyls such as n-pentyllithium and n-propyllithium and their sodium and potassium derivatives may be used in lieu of the n-butyllithium of EXAMPLE III. And finally, epichlorohydrin may be used in lieu of the epibromohydrin of EXAMPLE IV.

Methods of incorporating 1,1 '-bis( l-glycidoxyalkyl)- ferrocenes into solid rocket propellant grains are described in the following EXAMPLES. For convenience, l,1'-bis(1-glycidoxyethyl)ferrocene is designated as the ferrocene derivative incorporated.

EXAMPLE V l,l'-Bis( l-glycidoxyethyl)ferrocene as Curing Agent A mixture of 0.1 equivalent (109.5 g) carboxy terminated polybutadiene, 0.08 equivalent (14.6g) 1,1 bis( l-glycidoxyethyl)ferrocene, 0.02 equivalent (2.5 g) triepoxide, and 1 percent by weight chromium octoate was mixed under vacuum for 0.5 hour and then cured at 60C for 3 days. The cured sample was compared with one in which the 1,1'-bis(l-glycidoxyethyl)ferrocene was replaced with an equivalent amount of a standard curing agent, Union Carbide ERL 4221 (diepoxide) and which was cured under identical conditions. Both cured samples were rubbery materials. The sample utilizing 1,l '-bis( l-glycidoxyethyl)ferrocene was softer.

EXAMPLE Vl l,l'-Bis( l-glycidoxyethyl)ferrocene as Coating on Oxidizer Crystals Oxidizer crystals such as ammonium perchlorate are coated with l,1'-bis(l-glycidoxyethyl)ferrocene by.

Ingredient Weight Coated Ammonium Perchlorate 73 Aluminum Powder l5 Carboxy Terminated Polybutadiene l 1.5 Epoxy Curing Agent 0.5

The 1,l'-bis( l-glycidoxyalkyl)ferrocenes may also be used to coat fuels, such as aluminum, prior to incorporation into a propellant mix cycle.

EXAMPLE VII 1,1 '-Bis( l-glycidoxyethyl)ferrocene as Plasticizer Liquid 1,1'-bis(1-glycidoxyethyl)ferrocene is added to a propellant mix which may be of the following general formulation:

Ingredient Weight Ammonium Perchlorate 70 Aluminum Powder l5 Hydroxy Terminated Polybutadiene l0.5 Triisocyanate Curing Agent 0.5 l ,l '-Bis( l-glycidoxyethyl )ferrocene 4 The propellant mix is processed by well-known techniques. During the cure cycle the ferrocene derivative undergoes homopolymerization to yield a high molecular weight, nonmigrating compound.

While 1,1-bis(l-glycidoxyethyl)ferrocene has been used as a specific compound in the foregoing EXAM- PLES, it will be apparent to those skilled in the art that any of the other derivatives disclosed in this specification can be used with similar results.

What is claimed is:

1. A new composition of matter comprising a solid rocket propellant binder and a curing agent having the general formula:

wherein R is selected from the group consisting of H, and alkyls having the formulas CH C H C -,H C H s n G ISa 1 15 and s u- 2. A solid rocket propellant comprising a cured binder containing fuel and oxidizer particles and a homopolymer of a compound having the general formula:

wherein R is selected from the group consisting of H,

and alkyls having the formulas CH C 14 C l-l C l-l 5 11 C6H13, 1 15 and s n- 3. A propellant according to claim 2 wherein said homopolymer is coated on said oxidizer particles.

4. A propellant according to claim 2 wherein said homopolymer is coated on said fuel particles.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 5 DATED A ril 1,.1975

'NVENTOR(5) 3 Robert C. Corley et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the drawings, cancel all figures, including the figure on the cover page.

Signed and Skilled this fif ay of August1975 [SEAL] A lies I:

RUTH C. MASON C. MARSHALL DANN Arresting Officer ('mnmissr'mu'r of Parents and Trademarks UNITED STATES PATENT OFFICE @ERTTTTCATE 6F QURRECTTQN PATENT NO. 13, 74,957

DATED April 1, 1975 INVENTOWS) T Robert C. Corley et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Q

In the drawings, cancel all figures, including the figure on the cover page,

0 $1'gned and geaied this fifth Day 0? August 1975 {SEAL} Arrest:

RUTH C. MASON C. MARSHALL DANN Alu'slmg Officer (mnmissr'mwr uj'lurems and Trademarks 

1. A new composition of matter comprising a solid rocket propellant binder and a curing agent having the general formula:
 2. A SOLID ROCKET PROPELLANT COMPRISING A CURED BINDER CONTAINING FUEL AND OXIDIZER PARTICLES A HOMOPOLYMER OF A COMPOUND HAVING THE GENERAL FORMULA:
 3. A propellant according to claim 2 wherein said homopolymer is coated on said oxidizer particles.
 4. A propellant according to claim 2 wherein said homopolymer is coated on said fuel particles. 